At UCSD many investigators are now conducting research which requires the microscopical analysis of human and murine tumors and their cognate normal tissues. Others are examining the details of changes induced in embryonic and adult animals by genetic and epigenetic intervention, so as to understand the mechanisms regulating normal and neoplastic development. These investigators who are studying topics relevant to cancer need ready, affordable access to high quality histological and immunohistochemical technical services and to expert histopathological advice. This resource already provides pivotally important services to the Members of the Center and its importance will grow as it becomes more widely appreciated that microscopic evaluation of tissue is critical in cancer research.. This core services provides vital quality control of the presence of tumor tissue in a biopsy sample before biochemical or molecular biological analysis begins. Establishing the absence of tumor in tissue that is regarded as a normal control for such experiments is also confirmed. In addition, by utilizing the services of this core facility, a complete histologic (phenotypic) analysis of tissues from genetically altered mice, is made possible, from the embryo stage to the adult. Utilization of the services also allows a detailed analysis of the numerous mouse models of human cancer. The Histology Shared Resources provides high quality histology and immunohistochemistry services to all peer-reviewed Cancer Center members. It also liaises closely with other UCSD NCI-funded Cancer Center Shared Resources, especially Molecular Pathology, Transgenic Mouse and Digital Imaging, to create an interactive group of shared resources for research of tissue samples from human pathological specimens, from human pathological specimens, experimental animals carrying human xenotransplants, and genetically altered animals (Transgenic or "knock-out" mice).